Comparison Of Estimated Global Gross Primary Productivity And Evapotranspiration Based On Different Remote Sensing Data

Terrestrial ecosystem productivity,evapotranspiration is an important part of the global carbon and water circulations.Accurate estimation of terrestrial vegetation ecosystem productivity and evapotranspiration is an important way to determine the functions of terrestrial ecosystems and to understand the characteristics of ecosystem carbon and water circulations.In this study,we used the data from ground-based eddy covariance measuremens,the numerical forecast products of European Centre for Medium-Range Weather Forecasts(ECMWF),moderate-resolution imaging spectroradiometer(MODIS)product and Global Inventory Modeling and Mapping Studies(GIMMS)Leaf Area Index(LAI)data GIMMS LAI3 g to estimate and study the gross primary productivity(GPP),evaportranspiration(ET)and water use efficiency(WUE)for global terrestrial vegetation over 2001-2010,via the light use efficiency model and RS-PM model and then analyzed the spatio-temperal patterns of the gross primary productivity,evaportranspiration and water use efficiency.Main research work and achievements are summarized as follows:We also compared the global GPP and ET estimates during 2001–2010 by using the MODIS GPP algorithm,and MODIS ET algorithm based on the two global LAI products.The global GPP estimates based on GIMMS LAI3 g,MODIS15 LAI,are referred to as GPPLAI3 g,GPPMOD15 respectively.The global ET estimates based on GIMMS LAI3 g,MODIS15 LAI are referred to as ETLAI3 g,ETMOD15 respectively.We also compared remote sensing-based GPP and ET estimates with eddy covariance(EC)flux tower-measured GPP and ET.We analyzed spatio-temporal patterns and their correlations with the three GPP and ET estimates as well as the MODIS17 and MODIS16 product.The results showed the following.The o verall accuracy of the three global GPP estimates may be ranked as GPPMOD17 is higher than GPPLAI3 g,GPPMOD15 and ET estimates ranked as ETMOD16>ETLAI3g>ETMOD15.(3)In the global land area,GPP and ET reach a highest point in the equatorial low latitudes,reaching 2500 gC?mm-2?yr-1 and 1200 mm?yr-1,while the Evergreen Broadleaf Forest is higher than other biome types.In summary,compared to MO DIS15 LAI can only provide data from 2000 to date and there is a certain degree of accuracy,GIMMS LAI3 g is an effective product for GPP and ET simulation at the global scale,and thus,the long-term GPP and ET series estimated using the GIMMS LAI3 g and are reasonably acceptable.